Tensile bond strength of soft and hard relining materials to conventional and additively manufactured denture-base materials.

PURPOSE: Studies comparing tensile bond strength of various soft and hard denture liner materials to conventionally and additively manufactured denture base resins are lacking. The purpose of this study was to investigate the tensile bond strength between chair- and laboratory-side soft and hard relining materials and denture-base materials produced by additive manufacturing and conventional methods. MATERIALS AND METHODS: A total of 120 dimethacrylate-based additively manufactured and polymethylmethacrylate (PMMA)-based conventionally fabricated dumbbell-shaped denture-base resins were produced. Heat-cured laboratory-side soft reline material, self-cured chair-side soft reline material, and self-cured chair-side hard reline material were attached to the denture bases. The tensile force was applied to the specimens with a universal testing machine at a crosshead speed of 5 mm/min. The obtained data were analyzed with two-way ANOVA and post hoc Tukey tests. The significance level was set at α = 0.05. RESULTS: The highest tensile bond strength values were obtained in the specimens from the conventionally manufactured base and self-cured chair-side hard reline material group, and the lowest was seen in the additively fabricated base and self-cured chair-side soft reline material group (p < 0.001). Conventionally manufactured base material's tensile bond strength was higher than that of additively fabricated resin, and self-cured chair-side hard reline material's strength was higher than that of laboratory-side and chair-side soft reline materials (p < 0.001). However, no significant difference emerged between laboratory-side and chair-side soft reline materials (p = 0.405). CONCLUSIONS: All the specimens used in the present study had tensile bonding stress values for clinical use. Both denture base resins provided an increased bond to the chair-side hard relining material, although an improved bond did not emerge for the chair-side and laboratory-side soft denture reline materials.

Evaluating the Effect of Ambient and Scanning Lights on the Trueness of the Intraoral Scanner.

PURPOSE: To determine the influence of different scanning and ambient light conditions on the trueness values of an intraoral scanning (IOS) device. MATERIAL AND METHODS: The present study was conducted among 20 complete dentate volunteers. After making complete maxillary arch impressions with vinyl polysiloxane material, type IV dental stone was poured, and working casts were obtained. Then, the models were digitized using a dental laboratory scanner (LS) and standard tessellation language (STL) files were acquired. Full arch digital scans of the volunteers were also performed using an IOS device with 2 ambient light conditions (RL: room light, 1003 lux, and ZL: zero light, 0 lux) and 2 scanning light modes (blue [B] and white [W]). Twenty digital scans per group at each light condition were consecutively obtained. Discrepancy between the digital scans and digitized working casts was analyzed using a 3D inspection software. The obtained data were analyzed using one-way ANOVA and Tukey tests (α = 0.05). RESULTS: Significant differences were obtained among different light conditions for the IOS device (p ˂ 0.0001, F = 42.958 for positive deviations and F = 29.278, for negative deviations). The room light and blue mode (RLB) condition had the lowest deviation values compared with the other light conditions, followed by room light and white mode (RLW), zero light and blue mode (ZLB), and zero light and white mode (ZLW; p =  0.008, p Ë‚ 0.0001, and p Ë‚ 0.0001, respectively). CONCLUSION: Lighting conditions are effective in assessing the trueness of the digital impressions made with an IOS device. RLB conditions are recommended for taking a digital impression.

Radiopacity of Esthetic Post Materials: Evaluation with Digital Analysis Technique.

PURPOSE: To evaluate the radiopacity of five post materials using a digital image analysis method. MATERIALS AND METHODS: Twelve specimens from each post type (two zirconia and three fiber based) of 2 mm in thickness were obtained using a diamond blade mounted on a cutting machine, and digital radiographs were taken along with aluminum step-wedge and dentin discs under standard exposure conditions. The mean gray-values of specimens were measured using a computer graphics program. Data were analyzed using one-way ANOVA followed by Holm-Sidak multicomparison test (p = 0.05). RESULTS: The highest radiopacity was observed in custom zirconia (5.842 millimeters of equivalent Al [mmAl]), and the lowest value was detected with FRC-Postec (Ivoclar Vivadent) (1.716 mmAl). Significant differences were revealed between the radiopacity values among all groups (p < 0.05), except the Zr post materials (p = 0.56). CONCLUSIONS: All tested post materials had higher radiopacity than dentin. Further studies will be required to clarify optimum radiopacity properties of the post materials to provide a precise clinical observation.

Tensile Bond Strength between Soft Liners and Two Chemically Different Denture Base Materials: Effect of Thermocycling.

PURPOSE: The bond strength of soft denture liner to a recently introduced denture base resin after thermocycling has not been compared to traditional denture base materials. The objective of this study was to investigate the effects of thermocycling on the tensile bond strength of soft denture liners to two chemically different denture base resins, polymethyl methacrylate (PMMA) and urethane dimethacrylate (UDMA). MATERIALS AND METHODS: A total of 48 PMMA and UDMA tensile test specimens were fabricated by attaching two different soft denture liners (Molloplast-B, Permaflex) according to the manufacturers' instructions and assigned to two groups. Half of the specimens for each group were stored in water for 1 week, and the other half were thermocycled (5000 cycles) between baths of 5°C and 55°C. Specimens were mounted on a universal testing machine with a 5 mm/min crosshead speed. The data were analyzed with three-way ANOVA and post hoc Tukey-Kramer multiple comparisons tests (α = 0.05). RESULTS: The highest bond strength was measured in the specimens from the UDMA/Molloplast groups, and the lowest was seen in the PMMA/Permaflex group. No significant difference in bond strength was detected in PMMA/Permaflex groups after thermocycling (p = 0.082), whereas other groups exhibited significant differences after thermocycling (p < 0.05). CONCLUSIONS: Thermocycling decreased the bond strength values in both the PMMA and UDMA groups. Regardless of types of soft liners, PMMA specimens presented lower bond strength values than UDMA specimens, both before and after thermocycling.

Magnetic Flux Density of Different Types of New Generation Magnetic Attachment Systems.

PURPOSE: The purpose of this study was to analyze the static magnetic flux density of different types of new generation laser-welded magnetic attachments in the single position and the attractive position and to determine the effect of different corrosive environments on magnetic flux density. MATERIAL AND METHODS: Magnetic flux densities of four magnetic attachment systems (Hyper slim, Hicorex slim, Dyna, and Steco) were measured with a gaussmeter. Then magnetic attachment systems were immersed in two different media, namely 1% lactic acid solution (pH 2.3), and 0.9% NaCl solution (pH 7.3). Magnetic flux densities of the attachment systems were measured with a gaussmeter after immersion to compare with measurements before immersion (α = 0.05). The data were statistically evaluated with one-way ANOVA, paired-samples t-test, and post hoc Tukey-Kramer multiple comparisons tests (α = 0.05). RESULTS: The highest magnetic flux density was found in Dyna magnets for both single and attractive positions. In addition, after the magnets were in the corrosive environments for 2 weeks, they had a significant decrease in magnetic flux density (p < 0.05). No significant differences were found between corrosive environments (p > 0.05). CONCLUSION: The leakage flux of all the magnetic attachments did not exceed the WHO's guideline of 40 mT. The magnets exhibited a significant decrease in magnetic flux density after aging in corrosive environments including lactic acid and NaCl.

In vitro comparison of the cytotoxicity and water sorption of two different denture base systems.

PURPOSE: Denture base resins have the potential to cause cytotoxicity in vivo, and the mechanical properties of resins are affected by water sorption. There is a correlation between residual monomer and water sorption. Thus, the purpose of this study was to evaluate water sorption and cytotoxicity of light-activated urethane dimethacrylate (UDMA) denture base resin compared to a conventional heat-activated polymethyl methacrylate (PMMA) resin. MATERIALS AND METHODS: Two denture base resins, heat-activated PMMA (Meliodent) and light-activated UDMA (Eclipse), were used in this study. Cytotoxicity (5 × 1 mm(2) ) and water sorption (1 × 1 mm(2) ) specimens were made following the manufacturers' instructions (n = 10). Cytotoxicity tests of denture base resins were performed according to ISO10993-5:1999, and water sorption was evaluated according to ISO 1567:1997. ANOVA tests were employed for evaluating data (α = 0.05). RESULTS: There was no cytotoxic effect in either the PMMA or UDMA group. In addition, contrary to short-term water storage, a significantly lower water sorption value was shown for UDMA resins compared to PMMA resins in both 3- and 6-month storage periods (p = 0.043 and p = 0.002, respectively). CONCLUSION: The tested denture base materials adhered to the ISO standards for both cytotoxicity and water sorption. The cytotoxicity of the light-activated UDMA resin tested was statistically similar to that of the heat-activated PMMA resin; however, the UDMA resin exhibited decreased water sorption in long-term water storage.

Diet, microbiota, and colorectal cancer.

Colorectal cancer (CRC) is the third most common cancer in the world causing nearly 500,000 deaths every year. In addition to genetic background, environmental factors including diet and lifestyle are accepted as major contributors to adenoma and CRC development. Lifestyle factors include high BMI, obesity, and reduced physical activity. Growing interest and accumulating data on human microbiota implicate that host-microbe interplay has an important role in the development of metabolic, neoplastic, and inflammatory diseases. Findings from recent studies suggest that colon cancer risk is determined by the interaction between diet and gut microbiota. Dietary changes affect gut microbiota and conversely microbiota mediates the generation of dietary factors triggering colon cancer. Identification of the microbial communities associated with carcinogenesis is of crucial importance. Nowadays, with the evolvement of culture-independent molecular techniques, it has become possible to identify main bacterial species in healthy individuals, inflammatory conditions, and CRC. Some recent studies have shown the differences in intestinal microbiota between colon cancer patients and healthy individuals. Animal studies have provided a better understanding of interaction between pathobionts and symbionts in the development of colon cancer. There is no single causative organism identified in CRC; however, there is strong evidence that reduction of protective bacteria, increase in some bacteria (ie, fusobacterium members; Bacteroides/Prevotella), and age-related changes in microbiota have an impact on adenoma or cancer development. Future studies will enable us to understand procarcinogenic and anticarcinogenic mechanisms and give insights to rational manipulation of the microbiota with prebiotics, probiotics, or dietary modifications.

Detection of hepatic steatosis using the controlled attenuation parameter: a comparative study with liver biopsy.

OBJECTIVE: Measurements of controlled attenuation parameter (CAP) with transient elastography (FibroScan®; EcoSens SA, Paris, France) may provide an accurate noninvasive assessment of hepatic steatosis. Herein, we prospectively determined the accuracy of liver fat quantification with CAP values in patients with chronic liver diseases and compare the results with those of histological assessment of steatosis as reference standard. MATERIALS AND METHODS: We enrolled 50 Turkish patients with various forms of chronic liver diseases. All patients underwent both CAP assessment and ultrasonography-guided liver biopsy. RESULTS: On liver biopsy, 16 (32%) patients had S0, 12 (24%) had S1, 9 (18%) had S2, and 13 (26%) had S3. The CAP values increased significantly (p<0.001) for each steatosis stage on liver biopsy: S0, 222 dB/m; S1, 250 dB/m; S2, 270 dB/m; and S3, 318 dB/m. A cutoff value of 257 dB/m could distinguish significant steatosis (S2-S3) from S0 (Sn 89%, Sp 83%, positive likelihood ratio 5.33, negative likelihood ratio 0.13, AUROC=0.93). Multivariable analysis indicated that neither liver fibrosis (p=0.58) nor disease etiology (p=0.96) had a significant impact on the association between CAP and the stage of steatosis. CONCLUSION: The determination of CAP using transient elastography can represent an important step forward toward the goal of an "imaging liver biopsy".

Evaluation of cardiac function by two-dimensional speckle tracking echocardiography in ulcerative colitis patients.

PURPOSE: Although ulcerative colitis (UC) shows obvious similarities with other autoimmune diseases, cardiac consequences have not adequately introduced. The aim of our study was to evaluate left ventricular (LV) function in UC patients by using novel echocardiographic parameters. RESULTS: Forty-five UC patients (mean age 37, 18 female) and 90 age- and sex-matched healthy volunteers (mean age 40, 38 female) included in the study. The mean disease activity score according to partial Mayo score was 2.16 ± 2.13. Mean global longitudinal strain (GLS) and global longitudinal strain rate (GLSR) measurements were significantly lower (-21.16 ± 2.71 vs. -23.36 ± 3.34; p < 0.001 and -1.33 ± 0.24 vs. -1.43 ± 0.24; p = 0.037, respectively), whereas global circumferential (-22.67 ± 3.66 vs. -23.37 ± 3.99; p = 0.140) and global radial strain (43.07 ± 8.58 vs. 44.12 ± 9.32; p = 0.545) measurements of the LV were similar in patients with UC compared with controls. The correlation coefficient (r) between GLS and partial Mayo score was -0.578 (p < 0.001). CONCLUSION: Our study suggests that systolic cardiac deformation values are impaired in UC patients. Reduced GLS and GLSR might be an early indicator of cardiac involvement in this population.

Evaluation of the surface roughness of zirconia ceramics after different surface treatments.

OBJECTIVE: This study aimed to investigate the effects of different mechanical surface treatments of pre-sintered zirconium oxide (ZrO2) in an attempt to improve its bonding potential. MATERIALS AND METHODS: One hundred and twenty IPS e-max ZirCAD (Ivoclar Vivadent) pre-sintered zirconia blocks (7 mm diameter, 3 mm height) received six different surface treatments (n = 20): Group C was untreated (control); Group E was Er:YAG laser irradiated; Group N was Nd:YAG laser irradiated; Group SB was sandblasted, Group SN was sandblasted and Nd:YAG laser irradiated; and Group SE was sandblasted and Er:YAG laser irradiated. After the surface treatments, the average surface roughness (Ra, µm) of each specimen was determined with a profilometer, then all the specimens were sintered. The surface roughness values were analysed through one-way ANOVA and Tukey's test. Changes in the morphological characteristics of ZrO2 were examined through scanning electron microscopy (SEM). RESULTS: Sintered sandblasted, Er:YAG laser treatment, sandblasted + Er:YAG laser and sandblasted + Nd:YAG laser irradiation resulted in a rougher surface than the other treatments. CONCLUSION: Nd:YAG laser irradiation alone was not effective in altering the zirconia surface morphology.

Evaluation of surface roughness and bond strength of quartz fiber posts after various pre-treatments.

PURPOSE: Debonding at the post-adhesive interface is a major problem for quartz fiber posts. The objective of this study was to evaluate surface roughness and bond strength of quartz fiber posts after various surface treatments. MATERIALS AND METHODS: Sixty-six quartz fiber posts were randomly divided into six experimental groups (n = 11) including group C, untreated (control); group SB, sandblasted; group SC, silica coated; group HF, hydrofluoric acid-etched; group N, Nd:YAG laser irradiated; group E, Er:YAG laser irradiated. Surface roughness of the posts was measured before and after pre-treatment. They were then bonded to resin cement and tensile bond strength was determined in a universal testing machine. Furthermore, two-way ANOVA and post hoc comparison tests (α = 0.05) were performed on all data. RESULTS: The highest mean force value was observed in group SB and followed by group E. Tukey's HSD test showed that there was no statistical difference between group SB and group E (p = 0.673). The highest mean roughness value was observed in group SB and a significant difference was found between group SB and all other groups (p < 0.001). This study reveals that sandblasting and Er:YAG laser irradiation provided a significant increase in bond strength between quartz fiber posts and resin cement. CONCLUSIONS: Sandblasting or Er:YAG laser-irradiation of the surface of the quartz fiber post before cementation is recommended for increasing retention.

Adhesion between glass fiber posts and resin cement: evaluation of bond strength after various pre-treatments.

PURPOSE: To evaluate surface roughness and bond strength of glass fiber posts to a resin cement after various surface treatments. MATERIALS AND METHODS: Sixty individually formed glass fiber posts with a diameter of 1.5 mm and a length of 20 mm were used for this study. They were randomly assigned to six groups of pre-treatment (n = 10/group): Group C, untreated (control); Group SB, sandblasted; Group SC, silica coated; Group HF, hydrofluoric acid-etched; Group N, Nd:YAG laser irradiated; Group E, Er:YAG laser irradiated. Surface roughness of the posts was measured before and after pre-treatment. The posts were then bonded to resin cement and tensile bond strengths were determined in a universal testing machine. For statistical analysis, two-way ANOVA and post-hoc comparison tests (α = 0.05) were performed. RESULTS: The highest bond strength value was observed in group HF, followed by group SC. There was a statistically significant difference in bond strength between group C and groups HF, SC and E (p < 0.001, p = 0.002 and p = 0.041, respectively). Posts of group SB and group N showed the highest surface roughness. CONCLUSIONS: The findings of the present study reveal that hydrofluoric acid-etching, silica coating and Er:YAG laser irradiation provided a significant increase in bond strength between glass fiber posts and resin cement.

Effects of complete dentures on respiratory performance: spirometric evaluation.

OBJECTIVES: There is a lack of data regarding whether edentulous subjects should remove dentures during spirometric measurements or not. The purpose of this study is to determine influences of complete dentures on spirometric parameters in edentulous subjects. MATERIALS AND METHODS: A total of 46 complete denture wearers were included in this study. Respiratory functions of the subjects were evaluated by spirometric tests that were performed in four different oral conditions: without dentures (WOD), with dentures, lower denture only and upper denture only. Forced vital capacity (FVC), peak expiratory flow, forced expiratory volume in 1 s and forced expiratory flow between 25% and 75% were evaluated. The data were analyzed with Friedman, Wilcoxon and paired-samples t tests (α = 0.05). RESULTS: Significant differences were found between spirometric parameters in different oral conditions (p < 0.05). In all spirometric parameters, the most important significant differences were found between conditions WOD, FVC and with lower dentures (FVC), and WOD (forced expiratory volume in 1 s) and with upper dentures (forced expiratory volume in 1 s) (p < 0.001). CONCLUSION: It was observed that complete dentures may unfavourably affect spirometric values of edentulous subjects. However, current findings need to be confirmed with advanced respiratory function tests.

Effect of different chemical disinfectants on color stability of acrylic denture teeth.

PURPOSE: The purpose of this study was to evaluate the effects of chemical disinfectants on the color stability of acrylic denture teeth (ADT) via spectrophotometric analysis. MATERIALS AND METHODS: A total of 120 central ADT specimens were randomly assigned to eight experimental groups and immersed in the following solutions (n = 15). Tap water/control group (CON), neutral soap (NTS), 2% sodium hypochlorite (SHC1), 5.25% sodium hypochlorite (SHC2), sodium perborate (SPB), povidone-iodine (PVI), chlorhexidine gluconate (CHG), and glutaraldehyde (GTA). Color measurements of teeth were performed by spectrophotometry after 10, 30, 48, 72, 144, and 960 immersion cycles in each tested solution. Color differences (ΔE*) were then evaluated using the Commission Internationale D'Eclairage (CIE) L*a* b* color system. Furthermore, Kruskal-Wallis, Mann-Whitney U, and Friedman comparison tests (α = 0.05) were performed on all data. RESULTS: There were significant differences in ΔE* values (p < 0.05) among the eight experimental groups. In addition, the highest ∆E* values were obtained in group SHC2, followed, respectively, by the SHC1, CHG, SPB, PVI, NTS, and CON groups. CONCLUSION: All the chemical disinfectants used in the study affected the color values of ADTs. Furthermore, ΔE* values increased along with the number of immersion cycles and total immersion time.

Shear bond strength of denture teeth to two chemically different denture base resins after various surface treatments.

PURPOSE: Debonding of acrylic teeth from the denture base remains a major problem in prosthodontics. The objective of this study was to evaluate the effect of various surface treatments on the shear bond strength of the two chemically different denture base resins-polymethyl methacrylate (PMMA) and urethane dimethacrylate (UDMA). MATERIALS AND METHODS: Two denture base resins, heat-cured PMMA (Meliodent) and light-activated UDMA (Eclipse), were used in this study. A total of 60 molar acrylic denture teeth were randomly separated into four groups (n = 15), according to surface treatment: acrylic untreated (group AC), Eclipse untreated (group EC), treated with eclipse bonding agent (group EB), and Er:YAG laser-irradiated eclipse (group EL). Shear bond strength test specimens were prepared according to the manufacturers' instructions. Specimens were subjected to shear bond strength test by a universal testing machine with a 1 mm/min crosshead speed. The data were analyzed with one-way ANOVA and post hoc Tukey-Kramer multiple comparison tests (α = 0.05). RESULTS: The highest mean bond strength was observed in specimens of group EB, and the lowest was observed in group EC specimens. A statistically significant difference in shear bond strength was found among all groups (p < 0.001), except between groups EC and EL (p = 0.61). CONCLUSION: The two chemically different denture base polymers showed different shear bond strength values to acrylic denture teeth. Laser-irradiation of the adhesive surface was found to be ineffective on improving bond strength of acrylic denture teeth to denture base resin. Eclipse bonding agent should be used as a part of denture fabrication with the Eclipse Resin System.

Tensile bond strength of silicone-based soft denture liner to two chemically different denture base resins after various surface treatments.

This study evaluated the effect of various surface treatments on the tensile bond strength of a silicone-based soft denture liner to two chemically different denture base resins, heat-cured polymethyl methacrylate (PMMA), and light-activated urethane dimethacrylate or Eclipse denture base resin. PMMA test specimens were fabricated and relined with a silicone-based soft denture liner (group AC). Eclipse test specimens were prepared according to the manufacturer's recommendation. Before they were relined with a silicone-based soft denture liner, each received one of three surface treatments: untreated (control, group EC), Eclipse bonding agent applied (group EB), and laser-irradiated (group EL). Tensile bond strength tests (crosshead speed = 5 mm/min) were performed for all specimens, and the results were analyzed using the analysis of variance followed by Tukey's test (p = 0.05). Eclipse denture base and PMMA resins presented similar bond strengths to the silicone-based soft denture liner. The highest mean force was observed in group EL specimens, and the tensile bond strengths in group EL were significantly different (p < 0.05) from those in the other groups.

Effects of sandblasting and laser irradiation on shear bond strength of low-fusing porcelain to titanium.

PURPOSE: To investigate the bond strength of low-fusing porcelain to commercially pure titanium (Ti) that was laser irradiated with different levels of energy and sandblasted. MATERIALS AND METHODS: A total of 30 titanium rods (10 mm in length and 12 mm in diameter) were prepared. The rods were divided into three groups (n = 10) according to surface treatments: SB: sandblasted; L1: Nd:YAG laser irradiated at 100 mJ, 10 Hz, and 1 W; L2: Nd:YAG laser irradiated at 200 mJ, 10 Hz, and 2 W. After surface treatment, low-fusing porcelain was applied onto the titanium specimens according to the manufacturer's instructions, and these specimens were stored in distilled water at 37°C for 24 h. The shear bond strength test was performed at a crosshead speed of 1 mm/min. In addition, Kruskal-Wallis and Mann-Whitney U-tests were used to compare the bond strength results (α = 0.05). SEM and EDS analysis were also performed for one specimen of each group after the shear bond strength test to evaluate the nature of the fracture surface. RESULTS: Group L2 produced the highest shear bond strength among the groups. There was a statistically significant difference in shear bond strength between groups L1 and L2 (p < 0.001). Nevertheless, no significant difference was found between groups SB and L1. EDS analysis revealed that laser treatment reduced presence of oxygen on the surface of Ti. In contrast to the sandblasted specimens, laser-irradiated specimens showed predominantly adhesive failure. CONCLUSION: Laser treatment may be an alternative method to sandblasting for enhancing the bond strength of low-fusing porcelain to commercially pure titanium.

Evaluation of a self-adhering flowable composite in terms of micro-shear bond strength and microleakage.

PURPOSE: The objective of this study was to evaluate dentin bond strength and microleakage of a self-adhering flowable resin with or without adhesive resin. MATERIALS AND METHODS: Dentin pieces were randomly assigned to three groups (n = 10): Group OR (Optibond+Revolution Formula 2 Flow); Group VF (Vertise Flow); and Group OVF (Optibond+Vertise Flow). Then specimens were stressed in shear at a cross-head speed of 1 mm/min until the bond failed. Moreover, microleakage was determined by restoring Class V cavities. A statistical analyses was carried out using Mann-Whitney U and Kruskal-Wallis tests (p < 0.05). RESULTS: Group OVF specimens produced the highest mean shear bond strength. In addition, the results showed that the marginal seal in group VF was similar to that in group OR. CONCLUSION: Self-adhering flowable composite resin combined with adhesive resin provided stronger dentin bond strength and a better marginal seal than when it was used individually. VF is a useful material with an acceptable bond strength and marginal seal.

Effect of various surface treatments on the retention properties of titanium to implant restorative cement.

There are conflicting results in the literature and divergent manufacturers' recommendations concerning the retention properties of implant restorative cements, and they can provide inadequate retention of implants, especially short or single implants. The objective of this study was to investigate the effects of sandblasting and different types of laser irradiation on the interfacial bond between titanium and resin cement through shear testing. A total of 60 samples (10 mm in length and 12 mm in diameter) were cut from titanium rods. The samples were divided into four equal groups according to the surface treatment: control, sandblasted, Nd:YAG laser-irradiated, and Er:YAG laser-irradiated. After surface treatment, the implant restorative cements were applied to the titanium samples which were stored in distilled water at 37°C for 24 h. The samples were then subjected to shear bond strength testing using a universal testing machine with a crosshead speed of 1 mm/min. The data were analysed with the Kruskal-Wallis and Mann-Whitney U tests (α = 0.05). The highest mean bond strength was observed in the control group, followed by the sandblasted group. A statistically significant difference in shear bond strength was found between the sandblasted group and both the laser-irradiated groups (p < 0.05). The Nd:YAG laser-irradiated group had a higher mean shear bond strength than the Er:YAG laser-irradiated group. The treatments applied to the titanium surface did not improve the strength of the bond to the implant restorative cement.

Effect of Er:YAG laser application on the shear bond strength and microleakage between resin cements and Y-TZP ceramics.

The objective of this study was to investigate the effect of Er:YAG laser irradiation on shear bond strength and microleakage between resin cements and yttrium-stabilized tetragonal zirconia (Y-TZP) ceramics. Eighty disc specimens of Y-TZP ceramics (6 mm × 4 mm) were prepared. The specimens were divided into two groups according to surface treatment (control and Er:YAG laser-treated). The control and lased specimens were separated into two groups for shear bond strength test (n = 20), and microleakage evaluation (n = 10). Specimens were subjected to shear bond strength test by a universal testing machine with a crosshead speed of 1 mm/min. Specimens for microleakage evaluation were then sealed with nail varnish, stained with 0.5% basic fuchsin for 24 h, sectioned, and evaluated under a stereomicroscope. The data were analyzed with one-way ANOVA and post hoc Tukey-Kramer multiple comparisons tests (α = 0.05) for shear bond strengths and a two related-samples tests (α = 0.05) for microleakage scores. Higher bond strength values were found in the laser-treated groups compared to the control groups. Microleakage scores among the groups showed that the laser-treated specimens had lower microleakage scores than those of control specimens in the adhesive-ceramic interface. Roughening surface of Y-TZP ceramic by Er:YAG laser increased the shear bond strengths of ceramic to dentin and reduced the microleakage scores.